Recently I started my first serious attempt to build a fire hydrant game model but I'm having problems with my normal map. I made a low poly object and a high poly object to project the normal map of the high poly over the low poly and get nice details with less polys as in many video tutorials that I watched but when I finally did it I noticed some pixelation in the normal map. When I apply the normal map to the low poly model it looks really ugly and it lost the smooth transitions and details that have the high poly object. I need some tips about how to improve my normal map baking without loosing the smooth surfaces achieved with the high poly object.

I also need some tips about how to paint a rough metal texture over the high poly model so I can bake in the normal map.

In general if you want better textures you would want to use higher image resolution values , so when you make your UV's you would want to crank up the res size higher such as 1024 by 1024 or 2048 by 2048 and so on for better quality.

As far as tweaking normal maps and messing around with them you can probably do a very careful and very light tweaks using gimp or phpotoshop, i have used the clone tool to tweak some and it worked for me , another thing I used that worked for me was duplicating my normal map on a layer and using a grain merge to get some light details to show , but after that still you will need to tweak the settings in blender .